The long term goal of this research is to understand the control of mitochondrial ATP production during changes in cellular work both in normal and pathological states. A number of clinical disorders, such as those due to cardiac ischemia and hypertrophy are associated with defects in energy metabolism. The proposed studies rely on the application of NMR, to monitor levels of key metabolites in the intact organ, and molecular genetic techniques, to produce transgenic mice with altered enzyme content and distribution. The immediate aims of the proposed research are to use a transgenic mouse model expressing creatine kinase in liver to determine the relation between cellular ADP levels, mitochondrial NADH levels, and oxygen consumption in vivo. The transgenic liver expressing creatine kinase offers unique opportunities to study mitochondrial respiratory control. This mouse model allows quantitation of both mitochondrial NADH redox state and ADP concentrations in the same tissue. Data relating ADP, mitochondrial NADH and oxygen consumption will be obtained and then used to test the hypothesis that hormone stimulation of oxidative ATP production occurs due to increases in mitochondrial NADH To set the stage for studies using transgenic mouse hearts, we propose to establish a working mouse heart perfusion model and investigate the relation between work, oxygen consumption and high energy phosphates. Finally, experiments will be performed to understand the role of mitochondrial creatine kinase, an abundant cardiac enzyme central to energy metabolism. A transgenic mouse expressing mitochondrial creatine kinase in liver will be produced. The effects of mitochondrial creatine kinase on the control of oxidative ATP production will be assessed in order to test the hypothesis that mitochondrial creatine kinase alters the response of mitochondria to changes in ADP concentrations. The proposed work will lead to a greater understanding of mitochondrial respiratory control in normal tissues. This is one of the first attempts to combine NMR and molecular genetics to dissect out the quantitative control of a metabolic pathway. The lessons learned should, in the future, be applicable to help plan, monitor, and interpret human gene therapy protocols